The program on human herpesviruses deals with herpes simplex (HSV) and Epstein-Barr viruses (EBV). The objectives are a multifaceted, interactive study of the molecular organization of viral genes in the DNA, identification of viral genes involved in cell transformation, aspects of regulation of viral gene expression in productive infection, abortive infection and in "transformed" cells containing only a fraction of the genome. The program on endogenous C-type viruses in mammalian cells consists of three projects. First, studies on the immunological and biochemical characterization of C-type viruses recently isolated in this laboratory from several human, diploid fibroblast-like cell strains. Second, the mechanism of C-type virus induction by the halogenated pyrimidine analog, 5-bromodeoxyuridine will be examined in synchronized cell cultures of rat embryo cells. Third, we propose to analyze the RNA genome, molecular weight and subunit compositon of the putative human C-type virus. The viruses isolated from human cell strains will be further compared by chromatography of oligonucleotide digestion products.